I have been getting the following error when i apt-get update
Err http://extras.ubuntu.com trusty InRelease
Err http://extras.ubuntu.com trusty Release.gpg Unable to
connect to extras.ubuntu.com:http: Fetched 1,508 kB in 2min 5s (12.0
kB/s) Reading package lists... Done W: GPG error:
http://ppa.launchpad.net trusty Release: The following signatures
couldn't be verified because the public key is not available:
NO_PUBKEY 78414460095F1873 W: Failed to fetch
http://extras.ubuntu.com/ubuntu/dists/trusty/InRelease
W: Failed to fetch
http://extras.ubuntu.com/ubuntu/dists/trusty/Release.gpg Unable to
connect to extras.ubuntu.com:http:
W: Some index files failed to download. They have been ignored, or old
ones used instead.
I have no idea of how to solve this issue.